Your L7 S/N is close to mine, I would perform the grid current meter calibration step to verify the meter functionality which is supplied by a voltage divider network (1 ohm 12w resistor) into a 200ua meter movement.?
I used an adjustable current / voltage bench top power supply and my Fluke 87 DMM set to madc, I checked it with the Fluke and power supply first then I put the grid circuit in series, there is an adjustment on the metering board.?
My plate current meter has an external shunt on the back of the meter and can be checked in a similar way as the grid current setup + to test point ¡°A¡± (Orange wire near edge of board) and the return would be pin 6 on the rear connector for the
plate circuit.?
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On Jan 7, 2025, at 4:57?PM, amfone via groups.io <amfone20000@...> wrote:
?
Thanks Thomas its not the switches for the meter and other aspects of the meter forward watts reflected watts etc, it all works, lights are on etc. Pushing the Ep volts meter several times changes nothing what is happening
is I read 1600V no load in the CW position and 2300 in the SSB position, the supply is not the issue. I'm thinking its the meter shunts one of them anyway. As I read the schematic R8 through R15 are the shunts 2.2 Meg and 1/2 watt. I have those from Mouser
as of today. I have not opened the L7 but I believe they are located right behind the 3-500Z tubes in a clear sleeve probably made of woven glass pure fiber which acts like a heat resistant cover or its just heat shrink tubing.
Any info appreciated especially for anyone who has actually changed the shunts in an L7. The S/N on this L7 is 2960.
Thanks Tim
WB8UHZ
On Tuesday, January 7, 2025 at 03:20:43 PM EST, Clayton kk4iz via groups.io <kk4iz284@...> wrote:
I did check for shorts and loose wires. I clean the push buttons with a good contact clean ?but still no meter movement the lights do come on when pushed
On Jan 7, 2025, at 1:47?PM, Thomas W9TAB via groups.io <electron@...> wrote:
A good diagnostic check of the L7¡¯s Schadow push button switches is ¡°Does the accompanying light come on with each switch selection?¡±?
If not they might need cleaning.?
There are two sections for each switch, one for the indicator and the other for the function.?
On Jan 7, 2025, at 11:47?AM, amfone via groups.io <amfone20000@...> wrote:
?
Thank you to all for all of the good advice, much much appreciated!
Tim
WB8UHZ
On Monday, January 6, 2025 at 08:41:00 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
Your front panel pushbuttons may need a good cleaning.
On Mon, 6 Jan 2025 08:11:41 -0600
"Clayton kk4iz via groups.io" <KK4IZ284@...> wrote:
> I have a L-7 and neither meter is working. I have not checked to see if? the watt meeter works.
--?
73
-Jim
NU0C
73¡¯²õ
KK4IZ
Amateur Radio Operator
Warren Bryant?
124 Crestview Dr
Clanton,AL.??35045
Email:?KK4IZ284@...
Cell: 205-389-4170
Thomas W9TAB